The scars from nipple reduction surgery, like any other surgery, are permanent. However, the scarring for the surgery to reduce prominent nipples is usually very well tolerated.
You may be confusing this with surgery to reduce the areola, which is the dark area around the nipple. This produces a circular shaped scar around the areola and again this is permanent.
The appearance of this scar will vary based on the color of your skin, the technique used, and the amount of tissue that needs to be removed.
The best way to find out if you are a good candidate is to schedule a consultation with your surgeon. During that visit, you can also find out how much the procedure will cost.